From: Paul Hannah <[email protected]> Reply-To: "[email protected]" <[email protected]> Date: Tuesday, December 16, 2014 at 10:50 PM To: "[email protected]" <[email protected]> Subject: Re: [beagleboard] Sensing flowmeter / protecting analog input
> Yes, that sounds exactly like the device. > > Awesome, didn't even know such a beast existed. Will do my reading tonight. http://www.ti.com/lit/an/scea046/scea046.pdf Page 4 explains the concept. Regards, John > > > Thanks again, > Paul. > > On Wed Dec 17 2014 at 17:47:20 John Syn <[email protected]> wrote: >> From: Paul Hannah <[email protected]> >> Reply-To: "[email protected]" <[email protected]> >> Date: Tuesday, December 16, 2014 at 10:26 PM >> >> To: "[email protected]" <[email protected]> >> Subject: Re: [beagleboard] Sensing flowmeter / protecting analog input >> >>> John, >>> >>> Cheers, it's a Gicar 9.0.95.05g -- sits in a cafe-style coffee machine, >>> though this'll only be the first install and the others may be different >>> (but presumably similar) parts. >> OK, I couldn¹t find a data sheet, but I think this is a three pin device, >> GND, POWER (4.5 - 20V) and PULSE. If this is correct, then all you need is a >> resistor divider as you suggested and a schmitt trigger to clean up the >> signal and then feed this directly into one of the GPIO pins. The schmitt >> trigger should be powered from VDD_3V3B and enabled with SYS_RESETn. >> >> Regards, >> John >>> >>> On Wed Dec 17 2014 at 17:02:30 John Syn <[email protected]> wrote: >>>> >>>> From: Paul Hannah <[email protected]> >>>> Reply-To: "[email protected]" <[email protected]> >>>> Date: Tuesday, December 16, 2014 at 9:27 PM >>>> To: "[email protected]" <[email protected]> >>>> Subject: Re: [beagleboard] Sensing flowmeter / protecting analog input >>>> >>>>> John, >>>>> >>>>> Digital input, hadn't thought of that but it makes sense, but I'm even >>>>> less sure of myself in that arena... >>>>> >>>>> I have to admit first my electronics knowledge is very rusty... >>>>> >>>>> Maybe I can use a voltage divider after the diode/s to halve that 1.8v+ >>>>> down to a safe 1.0v-ish. >>>>> >>>>> My first thought here is to use a zener diode as in here >>>>> http://www.electronics-tutorials.ws/diode/diode42.gif) with a voltage >>>>> divider after. >>>>> >>>>> Is the reverse voltage low enough to be safe with the BBB? >>>>> >>>>> If not, what if I set up something like this, but make D_Z1 a normal diode >>>>> so that the reverse current is completely stopped? >>>>> >>>>> Again, not interested at all in the quality of the signal as long as I can >>>>> determine the number of cycles. >>>>> >>>>> Sorry for the electronics 101 questions, appreciate all your time. >>>> BTW, what is the flowmeter part number. Perhaps there is a much simpler way >>>> to interface this to the BBB. >>>> >>>> Regards, >>>> John >>>>> >>>>> Cheers, >>>>> Paul. >>>>> >>>>> On Wed Dec 17 2014 at 14:55:09 John Syn <[email protected]> wrote: >>>>>> >>>>>> From: William Pretty Security <[email protected]> >>>>>> Reply-To: "[email protected]" <[email protected]> >>>>>> Date: Tuesday, December 16, 2014 at 7:00 PM >>>>>> To: "[email protected]" <[email protected]> >>>>>> Subject: RE: [beagleboard] Sensing flowmeter / protecting analog input >>>>>> >>>>>>> Hmm >>>>>>> >>>>>>> Maybe a 1.8v zener ? >>>>>> >>>>>> I see this recommendation all the time, but it won¹t work. Look at fig 4 >>>>>> in this document for the zener voltage characteristics DDZ9678: >>>>>> >>>>>> http://www.diodes.com/datasheets/ds30410.pdf >>>>>> <http://www.diodes.com/datasheets/ds30410.pdf> >>>>>> >>>>>> You will see that the zener voltage is at 1.8v when the current is at >>>>>> 80uA, but at 100uA, the voltage exceeds the maximum allowed on the ADC >>>>>> input. The only way to deal with this situation is to use a proper signal >>>>>> conditioner. First start with the voltage range of the input and then >>>>>> scale that down with an op-amp. You can also offset the reference to deal >>>>>> with negative voltage inputs. >>>>>> >>>>>> To the OP, you are only using this for counting, why use ADC. Why not >>>>>> scale/condition the output of the hall-effect flowmeter and use a digital >>>>>> input? >>>>>> >>>>>> Regards, >>>>>> John >>>>>> >>>>>>> Or 1N4007¹s in series = 1.4V >>>>>>> >>>>>>> "No one could make a greater mistake than he who did nothing because he >>>>>>> could do only a little." >>>>>>> "All that is necessary for the triumph of evil is that good men do >>>>>>> nothing" Edmond Burke (1729 - 1797) >>>>>>> http://www.packtpub.com/building-a-home-security-system-with-beaglebone/ >>>>>>> book >>>>>>> <http://www.packtpub.com/building-a-home-security-system-with-beaglebone >>>>>>> /book> >>>>>>> >>>>>>> >>>>>>> From: [email protected] [mailto:[email protected] >>>>>>> <mailto:[email protected]> ] On Behalf Of Paul Hannah >>>>>>> Sent: Tuesday, December 16, 2014 9:09 PM >>>>>>> To: [email protected] >>>>>>> Subject: [beagleboard] Sensing flowmeter / protecting analog input >>>>>>> >>>>>>> Hi, >>>>>>> >>>>>>> >>>>>>> >>>>>>> I'm looking to build a system to sense 'steps' of a hall-effect >>>>>>> flowmeter. >>>>>>> >>>>>>> >>>>>>> >>>>>>> My first throught is to use a voltage divider and rectifier circuit to >>>>>>> get down to the 0-1.8v I need. >>>>>>> >>>>>>> >>>>>>> >>>>>>> The problem I have is that every install may potentially have a >>>>>>> different input voltage. >>>>>>> >>>>>>> >>>>>>> >>>>>>> I'm wondering if there's a simpler way to do this. I really only need to >>>>>>> clip the voltage between 0-1.8v, it doesn't matter if it spends 90% of >>>>>>> it's time clipped and throws away the negative half of the signal >>>>>>> completely as I'm only interested in a count. >>>>>>> >>>>>>> >>>>>>> >>>>>>> The current draw will be in the millivolt-range used by the adc input, >>>>>>> so it shouldn't need anything too heavy. >>>>>>> >>>>>>> >>>>>>> >>>>>>> My first thought is a simple voltage regulator set to 1.8v, but I don't >>>>>>> know enough about them to know whether it's a viable option or which to >>>>>>> choose. >>>>>>> >>>>>>> >>>>>>> >>>>>>> Any suggestions? >>>>>>> -- >>>>>>> For more options, visit http://beagleboard.org/discuss >>>>>>> --- >>>>>>> You received this message because you are subscribed to the Google >>>>>>> Groups "BeagleBoard" group. >>>>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>>>> an email to [email protected] >>>>>>> <mailto:[email protected]> . >>>>>>> For more options, visit https://groups.google.com/d/optout >>>>>>> <https://groups.google.com/d/optout> . >>>>>>> >>>>>>> >>>>>>> No virus found in this message. >>>>>>> Checked by AVG - www.avg.com <http://www.avg.com> >>>>>>> Version: 2015.0.5577 / Virus Database: 4253/8748 - Release Date: >>>>>>> 12/16/14 >>>>>>> >>>>>>> >>>>>>> No virus found in this message. >>>>>>> Checked by AVG - www.avg.com <http://www.avg.com> >>>>>>> Version: 2015.0.5577 / Virus Database: 4235/8735 - Release Date: >>>>>>> 12/14/14 >>>>>>> -- >>>>>>> For more options, visit http://beagleboard.org/discuss >>>>>>> --- >>>>>>> You received this message because you are subscribed to the Google >>>>>>> Groups "BeagleBoard" group. >>>>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>>>> an email to [email protected] >>>>>>> <mailto:[email protected]> . >>>>>>> For more options, visit https://groups.google.com/d/optout >>>>>>> <https://groups.google.com/d/optout> . >>>>>> >>>>>> -- >>>>>> For more options, visit http://beagleboard.org/discuss >>>>>> --- >>>>>> You received this message because you are subscribed to the Google Groups >>>>>> "BeagleBoard" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, send an >>>>>> email to [email protected] >>>>>> <mailto:[email protected]> . >>>>>> For more options, visit https://groups.google.com/d/optout >>>>>> <https://groups.google.com/d/optout> . >>>>> >>>>> -- >>>>> For more options, visit http://beagleboard.org/discuss >>>>> --- >>>>> You received this message because you are subscribed to the Google Groups >>>>> "BeagleBoard" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send an >>>>> email to [email protected]. >>>>> For more options, visit https://groups.google.com/d/optout. >>>> >>>> -- >>>> For more options, visit http://beagleboard.org/discuss >>>> --- >>>> You received this message because you are subscribed to the Google Groups >>>> "BeagleBoard" group. >>>> To unsubscribe from this group and stop receiving emails from it, send an >>>> email to [email protected]. >>>> For more options, visit https://groups.google.com/d/optout. >>> >>> -- >>> For more options, visit http://beagleboard.org/discuss >>> --- >>> You received this message because you are subscribed to the Google Groups >>> "BeagleBoard" group. >>> To unsubscribe from this group and stop receiving emails from it, send an >>> email to [email protected]. >>> For more options, visit https://groups.google.com/d/optout. >> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to the Google Groups >> "BeagleBoard" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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